Multiple Current Peaks Research Articles

Effect of chloride ion on the corrosion behavior of SiN stainless steel in concentrated hot nitric acid media

The effect of Cl− on the corrosion behavior of SiN stainless steel (SS) in simulating spent fuel reprocessing environment was systematically investigated. The results indicated that both cathodic and anodic behaviors of SiN SS were altered and multiple current peaks were observed as Cl− concentration increased. Meanwhile, there existed a critical Cl− concentration beyond which SiN SS transitioned from passive state to active dissolution state. Furthermore, a formulation for multiple current peaks was put forward based on mixed potential theory, and the corrosion mechanism in hot nitric acid with various Cl− concentrations was proposed involving the competitive adsorption of ions.

Ionic conductance oscillations in sub-nanometer pores probed by optoelectronic control

<h2>Summary</h2> Ionic Coulomb blockade is one of the ion transport phenomena revealing the quantized nature of ionic charges, which is of crucial importance to our understanding of the sub-continuum transport in nanofluidics and the mechanism of biological ion channels. Here, we report an experimental observation and plausible theoretical reasoning of ionic conduction oscillations. Our experiment is performed under confinement in sub-nanometer (sub-nm) MoS₂ pores with optoelectronic control enabled for active tuning of pore surface charges. Under this charge control, we measure the ionic current at fixed voltages and observe multiple current peaks. Our analytical discussions and molecular dynamics simulations further reveal that the conductance oscillations may originate from the multi-ion interaction at the pore entry, particularly the electrostatic repulsion of ions external to the pore by ions bound inside the pore. Our work adds a further understanding of ionic Coulomb blockade effect and paves the way for developing advanced ionic machineries.

Multiple current peaks and spatial characteristics of atmospheric helium dielectric barrier discharges with repetitive unipolar narrow pulse excitation

Atmospheric dielectric barrier discharges driven by repetitive unipolar narrow pulse excitation are investigated numerically by using one-dimensional fluid models. The one-dimensional simulation focuses on the effects of applied voltage amplitude, pulse repetition frequency, gap width and γ coefficient on the multiple-current-pulse (MCP) discharge. The results indicate that the MCP behavior will lead to the stratification of electron density distribution in axial direction. Traditional MCP manipulating methods, such as reducing the applied voltage amplitude, increasing the applied voltage frequency, adjusting the gap width, cannot regulate MCPs exhibiting in this work. Further analyses reveal that the increasing electric field of the cathode fall region is the basis for the emergence of MCP behavior.

Emission and absorption diagnostics of a diffuse dielectric barrier discharge with multiple current peaks in helium at atmospheric pressure

Dielectric barrier discharge (DBD) is a simple means to sustain low-temperature diffuse discharges at atmospheric pressure. As atmospheric pressure plasma processing requires DBDs to work under various operating conditions, even diffuse discharges are often observed to exhibit multiple current peaks. In this work, multiple current peaks helium DBD is obtained by adding small concentration of argon in a nominally pure helium discharge. As the concentration of argon increases, multiple current peaks emerge while the discharge remains diffuse. Absorption spectroscopy is used to record the evolution of the He(23S) metastable atom. In a nominally pure helium discharge He(23S) metastable atom can reach up to 6 × 1011 cm−3. Even if quenching of the He(23S) metastable atom by argon is very effective, He(23S) density is found to still rise above 1010 cm−3 in a multiple current peaks discharge with 1100 ppm of argon. Optical emission spectroscopy of He n = 3 levels is also used to gain insights about the electron temperature (Te) through the means of a collisional-radiative model. For the multiple current peaks discharge with 1100 ppm of argon concentration, Te reaches about 1.0 eV during the primary peak but only about 0.3 eV during the secondary peaks.

Dynamic Nanoparticle‐Substrate Contacts Regulate Multi‐Peak Behavior of Single Silver Nanoparticle Collisions

AbstractSingle nanoparticle collision (SNC) technology has attracted increasing attention to explore single nanoparticle electrochemistry. By improving the temporal resolution of electrochemical recording, several recent studies have uncovered the intermittent electron transfer processes during the SNC of single silver nanoparticles. The electrode current curve displayed multiple current peaks that were completely separated, instead of a single peak. In the present work, we employed surface plasmon resonance microscopy to monitor the collision and oxidation processes of single silver nanoparticles. Simultaneous optical and electrochemical recordings provided comprehensive capability to correlate the physical movement of nanoparticles (from optical signal) and the electron transfer activity (from electrochemical signal). While previous studies hypothesized the physical detachment of nanoparticles from the electrode due to electrostatic repulsion or Brownian motion, the optical imaging revealed that nanoparticles often remained in physical touch with the electrode even though no electron transfer was occurring. These results demonstrated that the electrical contact between nanoparticle and electrode, which could be rather stochastic due to thermal motion and micro‐convection, played critical roles in regulating the multi‐peak behavior of single silver nanoparticles.

Multi-Species, Multi-Reaction Model for Porous Intercalation Electrodes: Part I. Model Formulation and a Perturbation Solution for Low-Scan-Rate, Linear-Sweep Voltammetry of a Spinel Lithium Manganese Oxide Electrode

We formulate and implement a porous electrode model that includes multiple lithium-insertion species and associated electrochemical and homogenous reactions. This multi-species, multi-reaction (MSMR) model can account for the multiple current peaks observed in voltammetry data at slow scan rates and is also consistent with X-ray diffraction analysis of several different electrode materials. The MSMR model is used to simulate linear-sweep voltammetry data of a porous electrode of spinel lithium manganese oxide at different scan rates, and an analytic solution to these equations at very slow scan rates is given, based on a perturbation analysis. The greatest sensitivity at these slow scan rates is to the thermodynamic parameters, because the electrode is close to a state of dynamic equilibrium. The poor sensitivity to transport parameters means that it is not possible to distinguish between transport effects and a small amount of hysteresis that could be present in the slow-scan voltage measurements. These facts are illustrated using both the analytic solution and its comparison to numerical calculations. In Part 2, the analytic solution will be combined with numerical simulations at higher scan rates to complete the fitting process of transport, kinetic and thermodynamic parameters, along with a small amount of hysteresis.

静電気放電耐性試験における微小ギャップを伴う放電電流の測定と現象考察

In electrostatic discharge (ESD) immunity tests, it has empirically been known that contact discharge currents are enhanced by the existence of small air gaps between an ESD generator and equipment under test; however, its mechanism has not been well examined so far. In this study, to clarify the phenomena, we measured discharge currents through small air gaps from 30 µm to 1 000 µm in contact discharges of an ESD generator to an IEC current calibration target. As a result, we found that multiple current peaks appear depending on the gap length and test voltage as well, which are unlikely to occur in conventional contact discharge tests. It was also found that the contact discharge current with a small gap provides a faster rise time and larger current peak in comparison with normal contact discharge tests even at the same test voltage. A circuit approach was used to qualitatively explain the peculiar finding and revealed that the stray capacitances of the discharge electrode are first charged by a contact discharge test and then the accumulated charges are abruptly discharged due to the spark that occurs across a small gap, which gives faster rise time and larger current peaks.

Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air

Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20–200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

Nonlinear behaviors in a pulsed dielectric barrier discharge at atmospheric pressure

In this paper, the temporal nonlinear behaviors of pulsed dielectric barrier discharge in atmospheric helium are studied numerically by a one-dimensional fluid model. The results show that the common single-period pulsed discharge with two current pulses per single voltage pulse can take place over a broad parameter range. The rising and falling times of the voltage pulse can affect the discharge characteristics greatly. When the discharge is ignited by a pulse voltage with long rising and falling times, a single-period pulsed discharge with multiple current peaks can be observed. Under appropriate rising and falling times of the voltage pulse, a stable period-two discharge can occur over wide frequency and voltage ranges. Also this period-two discharge can exhibit different current and voltage characteristics with changing the duty cycle. With other parameters fixed, the pulsed DBD could be driven to chaos through period-doubling route by increasing either the falling time or the frequency of voltage pulse.

Dynamics behavior of homogeneous dielectric barrier discharge at atmospheric pressure

An experimental study on the dynamics behavior of homogeneous dielectric barrier discharge (HDBD) at atmospheric pressure is described in this paper. Two kinds of discharge mode, glow and Townsend discharge modes, can be easily identified according to the differential conductivity of current-voltage relationship in the ascent stage of discharge current for the atmospheric HDBD. A (three-dimensional) 3D phase space made by discharge current, gas gap voltage, and charge density of dielectric-plate surface was utilized in the study. By projecting the discharge evolution trajectory in the 3D space, the 3D trajectory of multiple current peaks discharge in atmospheric helium shows a limited cycle with convolutions and undergoes a series of bifurcation process; however, the 3D trajectory of atmospheric N2 HDBD is a limited cycle without any convolution and bifurcation process. In addition, the first ionization coefficient of working gas plays a key role to determine the discharge mode of atmospheric HDBD, the transition of discharge mode and the dynamics stability of atmospheric HDBD.

Multiple current peaks and mode conversion of atmospheric pressure glow dielectric barrier discharge in helium

Experimental research was performed on the multiple current peaks (MCP) in atmospheric pressure glow dielectric barrier discharge in helium. In a MCP discharge sequence, the next discharge pulse is always affected by the previous one. The accumulated charges on the dielectric plate play an important role in the MCP formation. In addition, two discharge modes, glow and Townsend discharge modes, can be observed in a MCP discharge sequence. The discharge mode tends to convert from glow to Townsend discharge mode when increasing the applied voltage, decreasing the gas gap and reducing driving frequency, respectively.

Multipeak behavior and mode transition of a homogeneous barrier discharge in atmospheric pressure helium

Numerical calculations and analyses are carried out to get a further understanding of the mechanism of the homogeneous barrier discharge with multiple current peaks per half cycle of the applied voltage in atmospheric helium by means of a one-dimensional fluid model, taking into account the primary processes of excitation and ionization. Multipeak behavior is governed mainly by the width of the discharge gap. In smaller gas gap, multiple current peaks are formed due to the increases of charge density deposited on dielectric surfaces leading to the enhancement of the induced electric field. Each current peak corresponds to a new temporally separated breakdown. The discharge modes in the case of multipeak are studied. Both Townsend and glow modes can be observed in multipeak discharge. The transition between two discharge modes is investigated in details within a wide parameter range. When the ionization level is high enough to induce the formation of a large positive space charge density near the cathode, the glow discharge occurs; otherwise, the discharge is Townsend.